1. Field
This disclosure relates generally to semiconductors, and more specifically, to charge pump circuits used in semiconductors.
2. Related Art
Integrated circuits typically use charge pump circuits to boost a supply voltage to a value that is greater than the supply voltage value. Charge pumps are advantageous for creating a boost supply because they can be implemented in an integrated circuit. Many different types of charge pump circuits have been described to accomplish this function. In memory circuits, such as FLASH memory, a circuit node is charged to an elevated voltage. The circuit node is subsequently discharged. FLASH memory circuits typically require large voltage swings between the read, programming and erase potentials. For example a boosted voltage of from fifteen to twenty volts is commonly required. The slew rate or rate of change in voltage may vary significantly over such large voltage ranges. A fast slew rate may couple noise into the memory array and disturb signals or stored data. An uncontrolled slew rate results in wasted power, such as when the oscillators runs at such a high clock rate that the boost capacitors can not be fully filled before boosting occurs. The variation also results in varying circuit operation due to an uncertainty as to how quickly a voltage transition will occur.